The present invention is an improvement over U.S. Pat. No. 7,261,153, issued to Plomp. Both the present invention as well as the Plomp patent are assigned to the same assignee and the Plomp patent is incorporated by reference.
It is known in the art to provide a bell-shaped resilient member to use as a seal to seal off a section of pipe so that the section can be tested with pressure. Such seals are normally constructed from reinforced elastomer and dimensioned so that when pressure is applied to the sealed off portion, the pressure causes the bell-shaped member to expand against the inner wall of the pipe and seal it. A mandrel is often used with such seal members.
Typically, such packer cups are made of an elastomer. It is necessary with relatively soft materials to reinforce the cup and often the reinforcing is metal embedded in the elastomer prior to vulcanization. Such cups are shown in published patent application U.S. 2003/0098153 and U.S. Pat. No. 3,450,412. In the latter patent, fingers of metal are provided which extend longitudinally in the sides of the cup. During use, the outer covering will often wear away exposing the metal reinforcement. In that case, movement of the cup within a well tube can bend the reinforcing material so that it snags within the tube, plugging it. In that case, it can be extremely expensive to open the pipe or tube, to retrieve the cup.
In U.S. Pat. No. 4,149,566 a test cup is provided which has a bell-shaped end, L-shaped metal-reinforcing ring segments embedded therein and an opposite tubular portion with an internal metal sleeve embedded therein. This patent describes a prior art cup constructed of an elastomer of two different hardnesses. It is described that the juncture between the two elastomers is a fault line and typically such a device fails along this line sooner than with other types of seals. It is also noted that the lower or belled end of the cup includes the softer of the two elastomers.
In U.S. Pat. No. 4,751,870 there is described a seal for oil and gas well swabs. The seals are primarily of rubber with a centrally located reinforcing tube of metal or plastic. In this patent however internal reinforcing ribs are provided to resist the tendency to expand under pressure against the walls of the pipe.
In U.S. Pat. No. 5,028,056 a composite material is described which is used to form a reinforced base for a pump piston. Resilient material is filled with reinforcing fibers to increase the stiffness of the seal.
In U.S. Pat. No. 4,129,308 the seal is mounted on a mandrel by a frangible backup ring. This assembly is intended to be broken up and left in the well hole and therefore does not include metal supports.
U.S. Pat. No. 7,261,153, issued to Plomp, also describes a packer cup for use in the sealing of the interior of a pipe under pressure. This packer cup, as particularly described in FIG. 3 includes a sleeve of an elastomeric material, such as polyurethane having two different densities and hardnesses. The top or lip portion of the sealing cup described in the Plomp patent is of a softer material so that it would expand under pressure to form a seal. A tubular bottom portion would be constructed from an elastomer which would be harder than the material of the top or lip portion. For example, the lip would have a density of approximately 1.07 and the tubular end of the sleeve would have a density of approximately 1.3. The hardness of the lip would be approximately 80-95 SHORE A and the hardness of the tubular end would be approximately 60 SHORE D. Furthermore, the cup could be provided with an optional sleeve, such as constructed from metal or molded in a polymer. The outer diameter of the bell-shaped portion would be slightly larger than the inner diameter of the pipe into which it is inserted, thereby allowing for a proper seal under pressure.
However, it has been found that the softer material at the top or lip of the packing cup does not abrade as quickly as the harder material at the bottom of the packing cup. Additionally, the interface between the softer material and harder material is prone to separation in some circumstances.